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Full text of "Circuits"

Automatic Lights for Desk Interior 



Make] Projects 

hhiiilH ho/ 1 !/ tuMaal/ chare r\icf*f\\tat* 



build, hack, tweak, share, discover,- 



Automatic Lights for Desk 



Interior 



Written By: Mahesh Venkitachalam 



TOOLS: 



Hot Glue gun & hot glue (1) 
Soldering iron (1) 



PARTS: 






MQSFETBS 170(1) 
Resistors. 470kQ m 
Reed relays (1) 
Wired) 
LED strips (1) 
Magnet (1) 
9V battery (1) 
Battery clip 9V(1) 



SUMMARY 

This is a simple circuit that uses a reed switch and a (MOSFET) transistor to turn an LED 
strip on and off. I hooked this up to my desk so that the lights come on and illuminate the 
inside of it when I open the door. 



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Automatic Lights for Desk Interior 



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Automatic Lights for Desk Interior 



Step 1 — Automatic Lights for Desk Interior 




• Hook up the reed switch, transistor, resistor, and the LED strip as shown in the circuit 
diagram. You can first do a prototype on a breadboard. 

• Test the circuit using a small magnet. 

• Once you are happy with the circuit, solder it on to a small piece of PCB. 

• Cut the LED strips into as many pieces as you need (mind that you cut at the gap between 
sets of LEDS connected in series), and attach them inside your desk drawer or cabinet 
using their self-adhesive strips. 

• You can use a small plastic box (I used one that paper clips are sold in) as an enclosure 
for your PCB and 9V battery. 

• You will need to find an optimal position for the magnet and enclosure so that the LEDs go 
off when the door is almost closed. Once you are happy with their locations, you can use 
some hot glue to hold them in position. 

• Please check the video for additional information on how I installed the circuit. I first used 
a BJT 2N2222 to design the circuit, but upon feedback from other users (like Spritetm), 
switched to a MOSFET (BS170) to fix the battery drain problem. 



This is a simple project that uses very inexpensive materials. You can use the idea of a 
magnetic switch for many other projects that require something to happen when a door opens. 

Watch the video here: 

http://www.youtube.com/watch?v=wFeQDVLr . . . 

This document was last generated on 201 2-1 2-24 04:24:22 PM. 



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